Epic knows it was on to a good thing with Horde Mode in Gears Of War 2. It's not just that tons of fans spent hours of time battling through 50 waves of Locust soldiers while the AI got progressively more difficult. The popularity of Horde is also shown by the fact that in the years since Gears of War 2's release, versions of the mode have popped up in numerous other shooters. You know you've had a good idea when competitors start pinching it. Really, Epic hardly needed to look to their fans to see they'd hit pay-dirt.

Still, the developer obviously took fan feedback to heart when they set about creating the Horde Mode for Gears of War 3 – or Horde 2.0 as it's known. Some of the major changes seem to have been made after watching how players behave in Horde matches with reference to how they defend choke points and how they work as a team. In some maps in the original Horde Mode, for example, players were fond of sticking shields into the ground to create barriers against the oncoming Locust soldiers. Rather than punishing players for that, Epic has taken this piece of in-game creativity to heart and allowed it to inform many of the numerous tweaks it's made to Horde 2.0.

Players start each Horde Mode match by building a command post at one point in the map. These areas are predetermined and appear as translucent green outlines. That done, players are then able fortify the area around the command post, with barriers, sentry guns, decoys and gun turrets. Once again, the places where they can put these items is predetermined, but naturally, the fortifications are positioned in sections of the map designed to optimise the players' defence.

The fortifications are also all upgradable. For example, barriers start off in the form of a rail of spikes across a section of path. Players can then upgrade these spikes, at first level to a roll of barbed wire, at second level to an array of electric lines which shock any enemies trying to cross them and the highest level, to a set of lasers. The sentry guns and gun turrets upgrades cause more damage and allow for more accuracy. The decoys simply become more robust and engage the Locust for longer periods of time.

Players pay for these fortifications and upgrades with cash they earn on the battlefield for every kill they make and every ally they revive. There's also the option to save up cash and buy a large, heavily armed battle-mech called a Silverback. Once this is brought on to the battlefield, though, it's not like survival turns into a cakewalk. The Silverback has absolutely no rear armour so players riding inside it will need the other members of their team to watch their backs.

This sense of teamwork is carried through nearly every aspect of Horde 2.0. Players can now trade weapons, give each other ammunition and cash and even pool their resources to beef up the fortifications around their command posts or buy that expensive Silverback. Of course, the reason to play nice with others is basic survival; if they don't work as a team, the players will die.

And surviving in Horde Mode is a little more difficult this time round. The basic structure of the mode is unchanged; players start off by reducing basic Locust foot soldiers to puddles of jam, but the size and toughness of their opponents increases with every wave. Then at the end of every 10 waves, there's a boss battle and the boss is always randomly generated. Players never know what sort of boss they're facing until it lands on the battlefield and it can be anything from a Lambant Bezerker, to a squad of Reavers to a massive Brumack lumbering into view.

So, as you can imagine, it pays to keep those fortifications in good repair, the ammunition well stocked and as much cash in the bank for emergencies as possible. On top of that, players are able to take part in mini-challenges which pop up in the odd wave – such as completing a certain number of headshots – to earn loot boxes, the contents of which are also randomly generated. They also have access to all the lovely new weapons from the multiplayer beta to help them. It all adds up to one of the best co-op multiplayers I've played all year.

Epic's design director, Cliff Bleszinski, is fond of saying in interviews that Gears of War 3 is a game he wants players to marry, not just date. From that one can infer he's not too keen to see copies of Gears 3 in the pre-owned racks at retailers anytime after its release. It's a smart sound byte, but on the evidence of the work that Bleszinski and Epic have put into Gears 3 thus far, it's quite clear he means it. Beast Mode, Horde 2.0 and the competitive multiplayer all seem in place. Now, if the campaign mode lives up the promise of the demo at Microsoft's press briefing, Gears Of War 3 could well be one of the best games of this year.